The present invention relates to an apparatus for removing residual toner, and more particularly to an apparatus for removing residual toner from a surface of a photosensitive member in an image transfer type electrostatic copying machine or from a surface of a dielectric member in an electrostatic printer or a facsimile apparatus.
As well known in the art, an electrostatic latent image is formed on the surface of photosensitive member or dielectric member by use of optical means or electrical means alone or by a combination of both and the thus formed latent image is developed with toner for subsequent transfer onto a copying paper. The transfer of developed image onto the copying paper is most commonly effected by a corona charging means and thereafter, the paper is fixed to become a permanent copy. While it may be said that during the transfer of the developed image onto the copying paper, most of toner forming said developed image is transferred onto the copying paper, some toner will remain on the surface and such residual toner must be removed completely from the surface of photosensitive member or dielectric member before proceeding further with the next image forming operation.
For this purpose, the copying machine or the printer described above generally includes therein an apparatus for removing residual toner and among the various removing apparatuses hithereto proposed, a fur brush type cleaning apparatus is most commonly used as it is quite effective to remove residual toner. U.S. Pat. No. 3,917,397 discloses an embodiment of such cleaning apparatus and includes in essence a rotatable fur brush in frictional brush engagement with the surface to be cleaned for removing residual toner therefrom and a dusting bar in abutting or interrupting relation to the brush bristles for dusting off toner adhered to the brush.
On the other hand, there has been a strong demand in recent years for speeding up the image forming operation in copying machines facsimile apparatus and in electrostatic printers. To meet this demand, cleaning speed must be increased similarly to clean more area in a given unit of time. However, the increase of cleaning speed has encountered an unexpected problem in that a phenomenon generally known as the filming phenomenon has been observed on the surface to be cleaned. This filming phenomenon is the formation of a thin layer of resin of toner on the surface of the photosensitive member or dielectric member. More specifically, resin which is the major constituent of the toner gradually fuses and adheres to the cleaning surface as the cleaning operations are repeated and forms a thin layer of fused resin or toner on the surface. This occurrence of the filming phenomenon causes various harmful effects, one of which is the shortening of the life of the photosensitive member because it becomes incapable of forming a fine electrostatic latent image.
In the above-described apparatus for removing residual toner, the fur brush should be rotated at high speed in order to meet the demand for high speed image formation. However, the inventor of present application has observed the occurrence of the filming phenomenon more remarkably with an increase of the rotating speed of the fur brush. To examine the cause of the occurrence of the filming phenomenon, various experiments were conducted and attained the result that the primary reason therefor is in insufficient removal of toner adhered on the fur brush by the dusting bar. In other words, residual toner removed by the fur brush from the cleaning surface was not sufficiently dusted off by the dusting bar and this has caused remaining toner on the brush to become fused gradually to form the thin layer of resin on the surface of the photosensitive member or dielectric member. Accordingly, some measures must be taken to improve the apparatus for removing residual toner in order to avoid the occurrence of the filming phenomenon.